Asymmetric Hillslope Retreat Revealed from Talus Flatirons on Rock Peak, San Tan Mountains, Arizona, United States: Assessing Caprock Lithology Control on Landscape Evolution

Jeong-Sik Oh, Yeong Bae Seong, Phillip H. Larson, Seong-Chan Hong and Byung Yong Yu

Annals of the American Association of Geographers, 2020, vol. 110, issue 1, 98-119

Abstract: Talus flatirons (TFs) are morphostratigraphic markers of prior talus deposition that are now disconnected from the active hillslope. Three generations of TFs (TF1, TF2, TF3) exist flanking a Sonoran Desert inselberg, Rock Peak, in a welded tuff caprocks-controlled landscape bounded by pediments. TFs at Rock Peak enable estimation of slope retreat rates through the application of cosmogenic 10Be, optically stimulated luminescence dating, and catchment-wide denudation rates (CWDR). We estimate disconnection of TF1 on Rock Peak at 88.9 ± 7.8 ka (northern slope) and 29.1 ± 2.5 ka (southern slope). Rates of hillslope retreat measure between 311.6 mm·ka−1 (northern slope) and 728.5 mm·ka−1 (southern slope). Asymmetry in retreat rates is consistent with CWDR, with southern slopes denuding ∼1.5 times faster. The asymmetry is interpreted as the result of the southward structural dip of strata present (>10°). Denudation rates on the summit of Rock Peak (54.3 ± 19.4 mm·ka−1 welded tuff; 111.2 ± 15.3 mm·ka−1 sandstone conglomerate) support interpretation that removal of welded tuff caprock accelerates denudation of this landscape and amplifies the impact of the structural dip. Given this, we interpret that Rock Peak will evolve into a rounded residual hill as pediments flanking the inselberg lengthen through time, similar to landforms observed in the surrounding landscape where the welded tuff and underlying sedimentary caprocks are no longer present. Using the range of slope retreat rates from Rock Peak, we provide a first estimate for the length of time necessary for pediments to form via hillslope retreat in the Sonoran Desert. Key Words: caprock, landscape evolution, pediment association, talus flatiron, 10Be exposure dating.

Date: 2020
References: Add references at CitEc
Citations:

Downloads: (external link)
http://hdl.handle.net/10.1080/24694452.2019.1624421 (text/html)
Access to full text is restricted to subscribers.

Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:taf:raagxx:v:110:y:2020:i:1:p:98-119

Ordering information: This journal article can be ordered from
http://www.tandfonline.com/pricing/journal/raag21

DOI: 10.1080/24694452.2019.1624421

Access Statistics for this article

Annals of the American Association of Geographers is currently edited by Jennifer Cassidento

More articles in Annals of the American Association of Geographers from Taylor & Francis Journals
Bibliographic data for series maintained by Chris Longhurst ().